Water film type front heat exchanger for desulfurization wastewater multi-effect evaporation system

Abstract

The utility model discloses a water film type front heat exchanger for a desulfurization waste water multi-effect evaporation system. A plurality of heat exchange tubes are arranged in a vertical shell-and-tube heat exchanger, a heating medium flows from the upper side to the lower side in a shell pass, the pipe diameter of a heating medium outlet is larger than or equal to that of a heating medium inlet, and a refrigerant flows from the lower side to the upper side in the shell pass; a perforated partition plate is fixedly mounted below the upper tube plate, the heat exchange tubes penetrate through the open holes, first gaps are formed between the heat exchange tubes and the walls of the open holes, the total sectional area of the minimum-width positions of all the first gaps is larger than the sectional area of the pipe diameter of a heating medium inlet, and a heating medium enters the first gaps from the upper portion of the partition plate and flows downwards along the outer walls of the heat exchange tubes from the first gaps. A layer of liquid film is formed on the outer wall of the heat exchange tube; a baffle ring is fixed above part of the holes, the heat exchange tube penetrates through the baffle ring, a second gap is formed between the outer wall of the heat exchange tube and the inner wall of the baffle ring, the second gap is larger than or equal to the first gap, and gas or non-condensed steam in the heating medium flows downwards from the second gap. The heat of the heating medium can be fully and quickly conducted into the refrigerant in the heat exchange tube, and vacuum conduction is facilitated.

Description

Technical Field

[0001] The utility model belongs to the technical field of desulfurized wastewater resource treatment, and particularly relates to a water film type pre - replacement heat exchanger for a desulfurized wastewater multi - effect evaporation system. Background Technique

[0002] In the application practice in recent years, the "thermal method" concentration mainly based on negative pressure evaporation technology has gradually taken the leading position in zero - discharge technology due to its low investment and operation costs. However, it is found in practice that in the technological process of the existing negative pressure evaporation technology for desulfurized wastewater, the secondary condensate water from the second - effect evaporator goes to the third - effect evaporation or directly to the end condensate water tank. The heat of the secondary condensate water is not better utilized, but also makes the water temperature in the condensate water tank remain high. Under the negative pressure suction of the vacuum pump, the condensate water evaporates in the condensate water tank, reducing the vacuum degree of the system, overheating the second - effect evaporator, and finally leading to scaling in the flash evaporation system and a sharp decline in production capacity. It is necessary to add a heat exchanger on the secondary condensate water pipe and use the incoming desulfurized wastewater for heat exchange, which can better cool the secondary condensate water and fully utilize the heat of the secondary condensate water. This kind of heat exchanger should adopt a shell - and - tube type, with the refrigerant wastewater flowing through the tube side and the hot - medium condensate water flowing through the shell side. The condensate water flows from the bottom of the second - effect evaporator to the end condensate tank by gravity, and the water flow is in a low - speed self - flowing state. The condensate water cannot fully and efficiently contact with the heat exchange tubes, and in this case, the heat exchange speed is relatively low, the efficiency is low, and the heat exchange area of the exchanger needs to be very large, increasing the investment.

[0003] In addition, for the traditional shell - and - tube heat exchanger, the outside of the heat exchange tubes is all filled with the hot - medium, resulting in too much waste of the heat transfer space, low efficiency, and the inability to conduct vacuum transfer from the heat exchanger to the end condensate tank. The secondary steam generated by the first - effect evaporation separator can only be condensed and generate vacuum by the heat exchange of the second - effect evaporator and the added traditional pre - replacement heat exchanger, so as to promote the evaporation of the first - effect evaporation separator. The vacuum degree formed in this way is small, and the evaporation capacity of the first - effect evaporation separator is smaller than that without the pre - replacement heat exchanger, resulting in a decline in the production capacity of the system. Content of the Utility Model

[0004] Aiming at the problems existing in the prior art that the condensate water flows from the bottom of the second - effect evaporator to the end condensate tank by gravity, the water flow is in a low - speed self - flowing state, the condensate water cannot fully and efficiently contact with the heat exchange tubes, the heat exchange speed is relatively low, the efficiency is low, the heat exchange area of the exchanger needs to be very large, and the traditional shell - and - tube heat exchanger wastes too much heat transfer space, has low efficiency, and cannot conduct vacuum transfer from the heat exchanger to the end condensate tank, the utility model provides a water film type pre - replacement heat exchanger for a desulfurized wastewater multi - effect evaporation system.

[0005] The purpose of the utility model is achieved in the following way:

[0006] A water film type pre - replacement heat exchanger for a multi - effect evaporation system of desulfurized wastewater. The water film type pre - replacement heat exchanger is a vertical tube - and - shell heat exchanger. Inside the heat exchanger, multiple heat exchange tubes are evenly fixed by upper and lower tube sheets. A heat medium inlet and a heat medium outlet are arranged between the upper and lower tube sheets. The heat medium flows through the shell - side from top to bottom, and the diameter of the heat medium outlet is greater than or equal to the diameter of the heat medium inlet. A refrigerant inlet and a refrigerant outlet are respectively arranged at the upper and lower heads of the heat exchanger. The refrigerant flows through the tube - side from bottom to top. A partition is fixedly installed below the upper tube sheet inside the heat exchanger. Openings with the same number as the heat exchange tubes are evenly arranged on the partition. The heat exchange tubes pass through the openings, and a first gap is formed between the outer wall of the heat exchange tube and the hole wall of the opening. The total cross - sectional area of the minimum width of all the first gaps is greater than the cross - sectional area of the heat medium inlet diameter. The heat medium is dispersed into the first gap from the upper part of the partition, and the heat medium flows downward along the outer wall of the heat exchange tube, forming a liquid film on the outer wall of the heat exchange tube. During the downward flow of the heat medium along the outer wall of the heat exchange tube, heat exchange occurs with the refrigerant inside the heat exchange tube. A retaining ring is fixed above the upper part of the openings on the partition. The heat exchange tubes pass through the retaining ring, and a second gap is formed between the outer wall of the heat exchange tube and the inner wall of the retaining ring. The second gap is greater than or equal to the first gap, and the gas or non - condensable gas in the heat medium flows downward through the second gap.

[0007] When the heat medium is water, the minimum width of the first gap between the outer wall of the heat exchange tube and the hole wall of the opening is 1 mm.

[0008] The total cross - sectional area of the minimum width of all the first gaps is greater than 2.5 times the cross - sectional area of the heat medium inlet diameter.

[0009] The number of retaining rings accounts for 15 - 20% of the total number of heat exchange tubes.

[0010] The shape of the opening is a cylindrical straight hole, a conical hole or a cylindrical hole.

[0011] There is no water - storing part on the pipeline from the heat medium outlet to the tail - end condensation tank.

[0012] Compared with the prior art, the beneficial effects of the present utility model are as follows:

[0013] 1. For the water film type pre - replacement heat exchanger used in the multi - effect evaporation system of desulfurized wastewater, a relatively thin liquid film layer is formed on the outer wall of the heat exchange tube by the heat medium. The heat of the heat medium can be fully and quickly conducted to the refrigerant inside the heat exchange tube. There is also a gap space between the water film layers of adjacent heat exchange tubes, and this gap space has vacuum transfer, making the heat medium cool down faster.

[0014] 2. The design of the retaining ring for the water film type pre - replacement heat exchanger used in the multi - effect evaporation system of desulfurized wastewater ensures that the vacuum generated by the vacuum pump in the tail - end condensation tank is smoothly conducted to the pre - replacement heat exchanger and the first - effect evaporation separator. Due to the good condensation effect of the water film type pre - replacement heat exchanger, a greater vacuum will be formed in the first - effect evaporation separator, which promotes the first - effect evaporation separator to increase the evaporation capacity and can improve the production capacity of the system. Description of the Drawings

[0015] Figure 1 is the structural schematic diagram of the present utility model.

[0016] Figure 2 is the schematic diagram of the opening on the partition board.

[0017] Figure 3 is the schematic diagram of fixing the retaining ring on the partition board. Specific embodiments

[0018] The present utility model will be further described below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present utility model and are not used to limit the scope of the present utility model. After reading the content of the present utility model, those skilled in the art can make various changes or modifications to the present utility model, and these equivalent forms also fall within the scope defined by the present utility model.

[0019] As Figure 1 shown, a multi-effect evaporation system for desulfurized wastewater is a water film type pre-replacement heat exchanger. The water film type pre-replacement heat exchanger is a vertical tube heat exchanger 10. Inside the heat exchanger, multiple heat exchange tubes 1 are uniformly fixed by upper and lower tube sheets 11. A heat medium inlet 12 and a heat medium outlet 13 are arranged between the upper and lower tube sheets. The heat medium flows through the shell side from top to bottom, and the diameter of the heat medium outlet is greater than or equal to the diameter of the heat medium inlet. A refrigerant inlet 14 and a refrigerant outlet 15 are respectively arranged at the upper and lower heads of the heat exchanger. The refrigerant flows through the tube side from bottom to top; a partition board 2 is fixedly installed below the upper tube sheet inside the heat exchanger. Openings 3 equal in number to the heat exchange tubes are uniformly arranged on the partition board 2. The heat exchange tubes 1 pass through the openings 3, and a first gap 4 is formed between the outer wall of the heat exchange tube and the hole wall of the opening. The total cross-sectional area at the minimum width of all the first gaps 4 is greater than the cross-sectional area of the heat medium inlet diameter. The heat medium is dispersed into the first gap 4 from the upper part of the partition board 2. The heat medium flows downward along the outer wall of the heat exchange tube from the first gap 4, and a liquid film is formed on the outer wall of the heat exchange tube 1. During the process of flowing downward along the outer wall of the heat exchange tube, the heat medium exchanges heat with the refrigerant inside the heat exchange tube; as Figure 3 shown, a retaining ring 6 is fixed above the upper part of the opening 3 on the partition board. The heat exchange tube 1 passes through the retaining ring 6, and a second gap 5 is formed between the outer wall of the heat exchange tube and the inner wall of the retaining ring 6. The second gap 5 is greater than or equal to the first gap 4. The gas or non-condensable gas in the heat medium flows downward through the second gap.

[0020] As Figure 2 shown in A, the shape of the opening 3 is a cylindrical straight hole or a conical hole. See Figure 2 B, and it can also be another cylindrical hole. The upper surface of the partition board and the hole wall of the opening are in fillet transition. See Figure 2 C. Figure 2 For the two openings shown in B and Figure 2 C, the upper width is greater than the lower width, and it is easier for the heat medium to flow into the first gap and form a liquid film on the surface of the heat exchange tube.

[0021] When the heat medium is water, the minimum width of the first gap 4 between the outer wall of the heat exchange tube and the hole wall of the opening is 1 mm, which can ensure that even when the water flow rate is small, it can touch the outer wall of the heat exchange tube to form a water film. A further preferred solution is that the water is condensed water. If the heat medium is other fluids, the size of this minimum gap needs to be determined through experiments according to the viscosity of the fluid.

[0022] The total area of the first gap 4 is more than 2.5 times the cross-sectional area of the heat medium inlet pipe diameter, ensuring that the heat medium can flow downward from the first gap 4 in the first place.

[0023] The number of retaining rings 6 accounts for 15 - 20% of the total number of heat exchange tubes 1. The heat medium liquid entering from the shell side flows along the first gap and forms a liquid film on the surface of the heat exchange tube 1. However, if all the first gaps are filled with the heat medium liquid, it will block the vacuum transmission, and a part of the steam and non-condensable gas that may exist in the heat medium cannot flow downward through the first gap, thus unable to exchange heat and cool down. By fixing the retaining rings 6 above some of the openings 3, it can ensure that when the liquid level of the heat medium is lower than the upper edge of the retaining ring, the heat medium liquid only passes through the first gap 4 and will not pass through the second gap 5, but the steam and non-condensable gas in the heat medium can pass through the second gap 5, and at the same time, the vacuum can be transmitted from the heat medium outlet pipe to the heat medium inlet pipe, which is conducive to vacuum transmission.

[0024] There is no water storage part on the pipeline where the heat medium outlet goes to the tail-end condensate tank. That is, the pipeline where the heat medium outlet goes to the tail-end condensate tank cannot have convex, concave or other water storage parts, ensuring that the condensed water in the heat medium outlet pipe can flow to the tail-end condensate tank by gravity when the condensed water in the heat medium outlet pipe is not full, so that the vacuum in the tail-end condensate tank can be conducted to the water film type pre-heat exchanger, which is beneficial to accelerating the cooling of the condensed water and the flow of the condensed water.

[0025] For the water film type pre-heat exchanger used in the desulfurization wastewater multi-effect evaporation system disclosed by the present utility model, a relatively thin liquid film layer is formed on the outer wall of the heat exchange tube by the heat medium, and the heat of the heat medium can be fully and quickly conducted to the refrigerant in the heat exchange tube. There is an interstitial space between the water film layers of adjacent heat exchange tubes, and this space has vacuum transmission, making the heat medium cool down faster. For the traditional shell and tube heat exchanger, the outside of the heat exchange tubes is all filled with the heat medium, and the thickness of the water layer between the heat exchange tubes is much thicker than the water film layer of the water film type, resulting in too much waste of the heat transfer space and low efficiency. If the same effect as the water film type is to be achieved, a larger heat exchange area is required.

[0026] In a traditional shell-and-tube heat exchanger, the outside of the heat exchange tubes is completely filled with the heating medium, and vacuum cannot be transmitted to the end condenser tank. The secondary steam generated by the first-effect evaporation separator can only be condensed by heat exchange with the second-effect evaporator and the additional traditional preheat exchanger to generate vacuum, which promotes evaporation in the first-effect evaporation separator. However, the vacuum degree formed in this way is small, and the evaporation capacity of the first-effect evaporation separator is even smaller than that without the preheat exchanger, resulting in a decrease in the production capacity of the system. In the structure of the water film type preheat exchanger, the design of the retaining ring ensures that the vacuum pump generated by the vacuum pump at the end condenser tank is smoothly conducted to the preheat exchanger and the first-effect evaporation separator. Due to the good condensation effect of the water film type preheat exchanger on the secondary steam generated by the first-effect evaporation separator, a greater vacuum will be formed in the first-effect separator, promoting the first-effect evaporation separator to increase its evaporation capacity and improving the production capacity of the system.

[0027] The above are only the preferred embodiments of the present invention. It should be noted that for those skilled in the art, without departing from the overall concept of the present invention, several changes and improvements can still be made, and these should also be regarded as the protection scope of the present invention.

Claims

1. A water film type front heat exchanger for a desulfurization wastewater multiple-effect evaporation system, characterized in that: The water film type front heat exchanger is a vertical shell and tube heat exchanger. A plurality of heat exchange tubes (1) are evenly fixed inside the heat exchanger through the upper and lower tube sheets. A heat medium inlet and a heat medium outlet are arranged between the upper and lower tube sheets. The heat medium enters from the top and exits from the bottom through the shell. The diameter of the heat medium outlet pipe is greater than or equal to the diameter of the heat medium inlet pipe. A refrigerant inlet and a refrigerant outlet are respectively arranged at the upper and lower heads of the heat exchanger. The refrigerant enters from the bottom and exits from the top through the tube. A partition (2) is fixedly installed below the upper tube sheet in the heat exchanger. The partition (2) is evenly provided with openings (3) having the same number as the heat exchange tubes. The heat exchange tubes (1) pass through the openings (3), and a first gap (4) is formed between the outer wall of the heat exchange tube and the wall of the opening. All the first gaps (4) The total cross-sectional area at the minimum width is larger than the cross-sectional area of ​​the heat medium inlet pipe diameter. The heat medium is dispersed from the upper part of the partition (2) into the first gap (4). The heat medium flows downward along the outer wall of the heat exchange tube from the first gap (4), forming a layer of liquid film on the outer wall of the heat exchange tube (1). During the process of the heat medium flowing downward along the outer wall of the heat exchange tube, heat is exchanged with the refrigerant in the heat exchange tube. A retaining ring (6) is fixed above the opening (3) on the upper part of the partition. The heat exchange tube (1) passes through the retaining ring (6). A second gap (5) is formed between the outer wall of the heat exchange tube and the inner wall of the retaining ring (6). The second gap (5) is larger than or equal to the first gap (4). The gas or non-condensable steam in the heat medium flows downward from the second gap.

2. The water film type front heat exchanger for the desulfurization wastewater multi-effect evaporation system according to claim 1, characterized in that: When the heat medium is water, the minimum width of the first gap (4) between the outer wall of the heat exchange tube and the wall of the opening is 1 mm.

3. The water film type front heat exchanger for the desulfurization wastewater multi-effect evaporation system according to claim 1, characterized in that: The total cross-sectional area of ​​all the first gaps (4) at the minimum width is greater than 2.5 times the cross-sectional area of ​​the heat medium inlet pipe diameter.

4. The water film type front heat exchanger for the desulfurization wastewater multi-effect evaporation system according to claim 1, characterized in that: The number of the retaining rings (6) accounts for 15-20% of the total number of the heat exchange tubes (1).

5. The water film type front heat exchanger for the desulfurization wastewater multi-effect evaporation system according to claim 1, characterized in that: The shape of the opening (3) is a cylindrical straight hole, a tapered hole or a cylindrical hole.

6. The water film type front heat exchanger for the desulfurization wastewater multi-effect evaporation system according to claim 1, characterized in that: There is no water storage area on the pipe from the heat medium outlet to the tail condenser tank.

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